you pose an interesting question, firstly I would have to agree that it would depend on a Master and his slave and what their relationship is about, what limits have been set between them as to how far a slaves wants to be taken.

For myself I think that in some instances a slave needs to be broken down before she can be rebuilt.

What use is a slave to a new Master when she is still governed by a former Masters training?

Yes, the line between pain & crueltry can be crossed.  I'm sure it is crossed often in many relationships.  O know I have.

The crossing is not as important as the aftermath.  "Will it be crossed again?"  Everybody goes too far, everybody makes mistakes.  It's how we deal with those mistakes that is important.

Masterlion pretty well sums it up.

I believe respect for Master/Slave is the answer.

Master Pop

If you are asking can I go to far with my slave then the simple answer is no! I may go farther then your Master will with you, or less as each relationship has its own parameters.

If you are asking can a Master go to far with his slave then perhaps. But who is the judge?

How far is to far each relationship has it's own boundaries.

Of course he can, but if the two of you have a commited relationship with the understanding that your only limits are the ones he has choosen for you, would it really matter? 

Someone said that to never cross the line is as dangerous as passing it.

Not everything is rational (this, from a too rational person seem a paradox). If both are balanced persons, bending the border a little bit will make both grow. Both, Master and slave.

No...If you are talking about a "true" Master and slave. He set's her limits and runs the relationship. Now your weekend warriors, or married to vanilla's and cheating with lifestyle people hoping not to get caught because they aren't even man enough to manage their own life and want to run other people's. Then yes. Anyone can "claim" to be a Master or a Masterful Man. But are they really? I can call my self the pope of Rome...doesn't mean its true...exept for in my own mind. I don't try to understand other people's relationship dynamics to often...it usually just gives me a head ache

Master Lion

If I wouldn't cross lines, I'd be perfect. Unfortunately it doesn't work that way. Even while being in an absolute M/s relationship, crossing lines will occurr. Misusing/abusing property simply happens, whether i's a slave, a car or a pencil.

In a relationship including respect or perhaps even love, crossing lines may be a terrible thing, depending on the situation. In a pure M/s relationship crossing lines may simply result in a (temporary) decrease of usefulness of the property, up to the property being absolutely useless.

In short, it depends on the type of relationship, agreements made beforehand. It also depends on who you are. Can you live with the knowledge that you have broken your property?